The invention relates to single-stage snowthrowers, and more particularly to a single-stage snow thrower having impeller assisted propulsion.
Powered walk-behind snowthrowers for consumer and commercial markets are well known. Such snowthrowers generally include a wheel supported body or frame having a housing with a generally open front, a pair of side walls, a rear wall and a discharge chute communicating with at least the rear wall. Single-stage snowthrowers are so named because they utilize a single powered implement, the impeller, for picking up and throwing snow outwardly away from the snowthrower. In contrast, two stage snowthrowers utilize two separate powered implements for handling snow, a low speed, high torque auger for breaking up and feeding snow rearwardly, and a high speed impeller for receiving the snow and throwing the snow outwardly.
Many dual stage snowthrowing machines are robust in dimension and weight, often defining swath widths of 24-32 inches. Dual stage machines often include a large internal combustion engine (6-15 hp) to supply power requirements for both the auger and impeller, in addition to the propulsion drive system. Dual stage snowthrowers may be propelled by engine driven rear wheels or tracks.
In comparison, single-stage snowthrowers have typically smaller swath widths and are lighter in weight. While single-stage snowthrower performance characteristics (snow volume per minute, throw distance, etc.) now approach those of dual stage models, single-stage models have typically not been propelled through driven rear wheels. Rather, contemporary single-stage snowthrowers have been propelled by the operator applying a manual force to push the snowthrower forward. As larger and more powerful single-stage snowthrowers are developed, the ability of the operator to manually propel the snowthrower will be diminished.
It has been recognized that the impeller of a single-stage snowthrower may be used as a xe2x80x9cdrivexe2x80x9d mechanism for assisting in propelling the snowthrower. The impeller of single-stage snowthrowers may include a flexible rubber element capable of engaging the ground surface during operation and developing a force tending to forwardly propel the snow thrower. The degree of ground engagement of the impeller (and thus the relative propulsion force developed by the impeller) may be increased by lifting the snowthrower by its handle thereby transferring a larger portion of the machine weight onto the impeller. Several conditions change as the handle is lifted by the operatorxe2x80x94an increasing portion of the impeller contacts the ground, an increasing downward (normal) force is developed across the impeller contact region, and a gap may develop between a lower scraper and the ground (leading to incomplete snow removal). Overall, while the resulting self propelling action is desirable, the forward tilting of the snowthrower requires constant user exertion to maintain the drive force. Additionally, the force necessary to tilt the snowthrower for propulsion assist of the impeller increases with the weight of the snowthrower. As larger, more powerful single-stage snowthrowers are developed, the ease of the operator to utilize the tilt drive-assist feature to propel the snowthrower will be diminished.
Another limitation of some prior single-stage snowthrowers related to the self propelled operation (via handle tilting to increase impeller normal force) is the difficulty in controlling the snowthrower along a straight path. Upon tilting the handle upwardly, the lower scraper and rear wheels break contact with the ground surface and the snowthrower may be supported entirely upon the ground through the rotating impeller. A force vector may be developed by the ejected snow creating a reactive moment force tending to rotate the snowthrower in a direction opposite the directed snow. In order to maintain the snowthrower along a straight path, the operator may be required to provide an opposing force at the handle. On a low friction surface such as ice, the snowthrower may be difficult to control and may xe2x80x9cskatexe2x80x9d or slide sideways upon the surface.
The present invention provides a single-stage snowthrower having a wheeled frame or undercarriage and an impeller which is movably coupled to the frame. An impeller housing includes a generally open front, a pair of side walls, a rear wall and a discharge chute. A handle extends outwardly to define an operator station during use of the snowthrower. A flexible rubber impeller is rotatably carried within the impeller housing and may be driven via a variety of power coupling strategies.
One aspect of the present invention is an impeller housing which is movably coupled relative to the handle portion of the snowthrower. The impeller may be placed in variable ground contact by movably displacing the impeller housing with respect to the handle portion.
Another aspect of the present invention is an impeller housing which is pivotally coupled to the frame of the snowthrower, wherein the impeller housing is pivotably coupled with respect to a pivot axis. In one embodiment, the pivot axis may be aligned in parallel with an axis of impeller rotation.
Another aspect of the present invention is the provision of an impeller housing to which the engine of the snowthrower is coupled. In this regard, both the impeller housing and the engine are movably coupled relative to the frame element of the snowthrower.
Yet another aspect of the present invention is the selective control of the impeller housing movement. The selective control of the impeller""s contact with the ground surface may be via a bail assembly adapted for user manipulation during machine operation. In one embodiment the bail assembly may control both the impeller housing movement and the clutch engagement for powering the impeller during operation.
Yet another aspect of the present invention is a single-stage snowthrower which may be propelled across the ground surface by the rotating impeller with the rear wheels remaining in contact with the ground surface. During impeller-associated self-propel operation, the ground contacting rear wheels promote machine stability and ease of use. Additionally, during operation on certain low friction surfaces, the ground engaging rear wheels may tend to counteract moment forces generated by the ejected snow.
Still another aspect of the present invention is a snowthrower having a bottom scraper element which displays a range of motion relative to the impeller housing. The bottom scraper may be flexibly coupled to the impeller housing to permit movement in response to ground surface contact.
Other features and advantages of the present invention will become apparent to those of ordinary skill in the relevant arts upon review of the following detailed drawings, description of preferred embodiments, and claims.